Cárdenas Hinojosa Gustavo, de la Cueva Horacio, Gerrodette Tim, Jaramillo-Legorreta Armando M
Departamento de Biología de la Conservación, Centro de Investigación Científica y de Educación Superior de Ensenada, Ensenada, Baja California, México.
Comisión Nacional de Áreas Naturales Protegidas, Secretaría de Medio Ambiente y Recursos Naturales, Ensenada, Baja California, México.
PeerJ. 2020 May 20;8:e9121. doi: 10.7717/peerj.9121. eCollection 2020.
Baseline knowledge of spatial and temporal distribution patterns is essential for cetacean management and conservation. Such knowledge is particularly important in areas where gillnet fishing occurs, as the Upper Gulf of California, which increases the probability of bycatch of cetaceans. In this area, the vaquita porpoise () has been widely studied, but the knowledge of other cetaceans is scarce and based on traditional visual survey methods. We used data collected by an array of acoustic click detectors (C-PODs) during the summers 2011 to 2015 to analyze the distribution of dolphins in the Vaquita Refuge in the Upper Gulf of California. We recorded 120,038 echolocation click trains of dolphins during 12,371 days of recording effort at 46 sampling sites. Based on simultaneous visual and acoustic data, we estimated a false positive acoustic detection rate of 19.4%. Dolphin acoustic activity varied among sites, with higher activity in the east of the Vaquita Refuge. Acoustic activity was higher at night than during the day. We used negative binomial generalized linear models to study the count of clicks of dolphins in relation to spatial, temporal, physical, biological and anthropogenic explanatory variables. The best model selected for the response variable included sampling site, day-night condition, and vertical component of tide speed. Patterns in the spatial distribution of predicted acoustic activity of dolphins were similar to the acoustic activity observed per sampling season. Higher acoustic activity was predicted at night, but the tide speed variable was not relevant under this condition. Acoustic activity patterns could be related to the availability of prey resources since echolocation click trains are associated with foraging activities of dolphins. This is the first study of the distribution of dolphins in Mexico using medium-term systematic passive acoustic monitoring, and the results can contribute to better management to the natural protected area located in the Upper Gulf of California.
了解时空分布模式的基线知识对于鲸类动物的管理和保护至关重要。在刺网捕鱼发生的地区，如加利福尼亚湾上游，此类知识尤为重要，因为这会增加鲸类动物误捕的可能性。在该地区，小头鼠海豚已经得到了广泛研究，但对于其他鲸类动物的了解却很匮乏，且基于传统的目视调查方法。我们利用2011年至2015年夏季一系列声学咔哒探测器（C-PODs）收集的数据，分析了加利福尼亚湾上游小头鼠海豚保护区内海豚的分布情况。在46个采样点进行了12371天的记录工作，期间我们记录到了120038次海豚的回声定位咔哒序列。基于同步的目视和声学数据，我们估计声学检测的误报率为19.4%。海豚的声学活动在不同地点有所不同，在小头鼠海豚保护区东部活动更为频繁。声学活动在夜间高于白天。我们使用负二项广义线性模型来研究海豚咔哒声计数与空间、时间、物理、生物和人为解释变量之间的关系。为响应变量选择的最佳模型包括采样点、昼夜条件和潮汐速度的垂直分量。预测的海豚声学活动空间分布模式与每个采样季节观察到的声学活动相似。预计夜间声学活动较高，但在此条件下潮汐速度变量并不相关。声学活动模式可能与猎物资源的可用性有关，因为回声定位咔哒序列与海豚的觅食活动相关。这是首次利用中期系统性被动声学监测对墨西哥海豚分布进行的研究，研究结果有助于更好地管理位于加利福尼亚湾上游的自然保护区。
